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Pitting on 15 year old boat.


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3 hours ago, Keith M said:

There is growing evidence that a GI can be switch on by stray current within the supply circuit.

The correct solution is either a Isolation or Polarization  Transformer.

 

Check out the Smartgauge web site.

But but but 

Certain members of this forum past and present proved conclusively that wasn't the case.

 

Personally I have an IT as I have never trusted diodes, I seem to have a terrible pain in the diodes down in my left side.

I can't see how a Polarization Transformer can help with galvanic corrosion as it doesn't isolate the boat PE from the supply.

 

Edited by Loddon
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My boat used to have shore line to run a battery charger, whilst in the marina unused,  GI fitted and tested ok.

Now after fitting solar panels, and removing the shore line, should I expect reduced or stopped Galvanic corrosion?

 

Bod.

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1 hour ago, Loddon said:

I can't see how a Polarization Transformer can help with galvanic corrosion as it doesn't isolate the boat PE from the supply.

Wtf is a Polarization Transformer?

 

I googled it and discovered that...

In its most general form, the polarization transformer comprises an input phase shifter for varying the relative phase between orthogonally polarized components of the incident wave, a mode converter for varying the relative magnitudes of said orthogonally polarized wave components, and an output phase shifter

 

So I repeat, what is a Polarization Transformer?

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13 minutes ago, WotEver said:

Wtf is a Polarization Transformer?

 

I googled it and discovered that...

In its most general form, the polarization transformer comprises an input phase shifter for varying the relative phase between orthogonally polarized components of the incident wave, a mode converter for varying the relative magnitudes of said orthogonally polarized wave components, and an output phase shifter

 

So I repeat, what is a Polarization Transformer?

I had no idea but mr google says;

 

In a polarization transformer the green safety grounding wire that comes aboard the vessel from the dock, inside the shorepower cord, is connected to the vessel’s own green safety grounding, bonding and DC negative systems (i.e., shore and vessel grounds are common.) Hold that thought, it’s important.

Polarization transformers ensure, as the name implies, that the polarity of the electricity that is provided to the boat is correct. Therefore, if the polarity of the wiring on the dock is somehow compromised, the neutral and hot wires are reversed (“neutral” and “hot” are, roughly speaking, the alternating current or AC equivalent of direct current, or DC, “ground” and “positive”) for instance, once passing through the transformer the fault is corrected.

 

https://www.passagemaker.com/technical/the-ins-and-outs-of-shorepower-transformers

 

 

Without adding a GI it doesn't seem to do much for isolation.

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Reading the above, they’re the same thing. The only difference is in how the earth connection is made, with one method being pointless.
 

The argument made in the article about the transformer case becoming live is of course moot with the Airlink’s plastic casing. 

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7 hours ago, Loddon said:

But but but 

Certain members of this forum past and present proved conclusively that wasn't the case.

 

Personally I have an IT as I have never trusted diodes, I seem to have a terrible pain in the diodes down in my left side.

I can't see how a Polarization Transformer can help with galvanic corrosion as it doesn't isolate the boat PE from the supply.

 

I wouldn't put a diode in my earth wire, its the most important of the three

 

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5 hours ago, Loddon said:

I had no idea but mr google says;

 

In a polarization transformer the green safety grounding wire that comes aboard the vessel from the dock, inside the shorepower cord, is connected to the vessel’s own green safety grounding, bonding and DC negative systems (i.e., shore and vessel grounds are common.) Hold that thought, it’s important.

Polarization transformers ensure, as the name implies, that the polarity of the electricity that is provided to the boat is correct. Therefore, if the polarity of the wiring on the dock is somehow compromised, the neutral and hot wires are reversed (“neutral” and “hot” are, roughly speaking, the alternating current or AC equivalent of direct current, or DC, “ground” and “positive”) for instance, once passing through the transformer the fault is corrected.

 

https://www.passagemaker.com/technical/the-ins-and-outs-of-shorepower-transformers

 

 

Without adding a GI it doesn't seem to do much for isolation.

I am glad you googled that. I would suggest its an isolating transformer with the secondary neutral pinned down the the boat earth conductor so that neutral on the boat is always at hull potential and the live is always 110/ 240 above it.

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I have always had an odd thought. If you have a boat with a GI or an IT and you moor in a marina and the two boats either side of you do not have GIs or ITs and they have poor blacking and stray currents are flowing between them, can your hull end up forming part of the circuit, therefore suffering galvanic corrosion even though your earth is isolated from the hull. This would also apply if you were not connected to shore power but both your neighbours were without isolation. If this thought is true, then it means you need to keep your blacking in good condition.

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40 minutes ago, ditchcrawler said:

I am glad you googled that. I would suggest its an isolating transformer with the secondary neutral pinned down the the boat earth conductor so that neutral on the boat is always at hull potential and the live is always 110/ 240 above it.

But that's exactly how an Isolating Transformer is wired. 

 

The only difference with this so-called 'Polarization' transformer is that the shore earth lead is also bonded to the hull, making the whole exercise pointless.  Its sole purpose appears to be to correct a reversed L-N connection on the shore bollard; something which rarely if ever happens in the UK and which can be simply indicated with a 'Reverse Polarity' indicator.

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7 minutes ago, WotEver said:

What is it that you want explaining?  I described its function in  post #36

 

I would love an explanation about the GI conduction issue as I thought this had been put to bed years ago by various forum members ;)

 

For the avoidance of doubt I have an IT, one of the first Airlink ones (2006) and would not use a GI.

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59 minutes ago, Loddon said:

I would love an explanation about the GI conduction issue...

My understanding is that it’s a non-issue.
 

What concerns me more is that there will always be a small leakage current through diodes, although it could well be in the order of microamps. Whether that tiny leakage is of any significance is doubtful but of course an IT completely eliminates any connection whatsoever. 

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6 minutes ago, WotEver said:

My understanding is that it’s a non-issue.
 

What concerns me more is that there will always be a small leakage current through diodes, although it could well be in the order of microamps. Whether that tiny leakage is of any significance is doubtful but of course an IT completely eliminates any connection whatsoever. 

What bothers me is if it goes open circuit there is no leakage and no earth, but I am old fashioned 

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3 minutes ago, ditchcrawler said:

What bothers me is if it goes open circuit there is no leakage and no earth, but I am old fashioned 

From a safety perspective I agree. I was more referring to their functionality as corrosion-prohibitors ;)

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